The present invention relates to a synchronizing device in a vehicle gearbox, comprising a guide sleeve, intended to be non-rotatably joined to a shaft in the gearbox, an engaging sleeve, which is non-rotatably but axially displaceably mounted on the guide sleeve, an engaging ring provided with external engaging teeth, said ring being intended to be solidly joined to a gear rotatably mounted on the shaft and be lockable relative to the guide sleeve by axial displacement of the engaging sleeve from a neutral position to an engagement position, in which internal engaging teeth on the engaging sleeve engage the external teeth on the engaging ring, and synchronizing means cooperating with the engaging sleeve and the engaging ring in the form of at least two concentric synchronizing rings each having a conical frictional surface, said rings being movable into engagement with opposing conical frictional surfaces on a synchronizing cone lying between the synchronizing rings and being fixed rotationally relative to the engaging ring, the one synchronizing ring being fixed rotationally relative to the other synchronizing ring by means of an annular torque-transmitting element.
Synchronizing devices of the above mentioned type, so-called double synchronizers, are used i.a. in gearboxes for trucks in order to increase the synchronizing torque and thus reduce the work of shifting and make possible short movement of the shift lever when shifting. A double synchronization provides approximately 30% reduction in the shifting force on the shift lever, compared with a corresponding single synchronization, and also permits steeper locking angles, which facilitates release after completed synchronization.
In a synchronizing device of the type described by way of introduction, which is known, for example, by Swedish Lay-Open Print 448 182, the torque-transmitting element is an annular sheet metal disc, which is provided with radial projections which engage in notches in the respective synchronizing ring. The metal disc lies completely to one side of the guide sleeve in a gap between it and the synchronizing rings, which means that each metal disc in the gearbox increases the axial length of the gearbox with its thickness plus the required play between the disc and the adjacent components in comparison with a corresponding gearbox with single synchronization.
The purpose of the present invention is to achieve a gearbox with double synchronization, the length of which does not need to be greater than a corresponding gearbox with single synchronization, so that a manufacturer of, for example, both types of gearboxes can use a number of common components therefor.
This is achieved according to the invention by virtue of the fact that the torque-transmitting element has, firstly, driver fingers extending from its outer periphery radially and sunk into the guide sleeve, said driver fingers being received in notches in the guide sleeve, and, secondly, has first driver elements engaging in notches in the outer synchronizing ring and second driver elements engaging in notches in the inner synchronizing ring.
In a synchronizing device made in this manner, the torque transmitting element does not require any extra axial space, since its driving projections are sunk in the guide sleeve. This also means that the axial length of the synchronizing rings can be increased in a given gearbox compared to the solution shown in the Swedish Lay-Open Print 448 182, thus increasing the frictional surfaces and thereby the transmitting capacity.